1. Field of the Invention
This invention relates to a centrifugal apparatus for rotating a rotor with protection.
2. Description of the Prior Art
A centrifugal apparatus with protection comprising a rotor, a driving motor for rotating the rotor, a detector for detecting a rotation speed of the rotor, and a controller for protecting against overspeed running of the rotor in response to the detector is known. FIG. 9 is a bock diagram of a prior art centrifugal apparatus with protection disclosed in U.S. Pat. No. 4,903,191. An exchangeable rotor 201 is rotated by a motor 202. Rotation of the exchangeable rotor 201 is detected by a detector 204 by detecting a magnet field from a magnet fixed to the exchangeable rotor 201. A master microprocessor (mpu) 211 and a slave microprocessor 205 separately detect the rotation speed of the exchangeable rotor 201 and the kind of the exchangeable rotor 201. If either of the master microprocessor 211 or the slave microprocessor 205 detects overspeed running of the exchangeable rotor 201 in accordance with the detected kind of the exchangeable rotor, that is, either of the master microprocessor 211 or the slave microprocessor 205 detects whether the rotation speed of the exchangeable rotor 202 exceeds a maximum value determined in accordance with the detected kind of the exchangeable rotor, an overspeed protection signal is supplied to an overspeed protection switch for cutting off drive signals to the motor 202. Therefore, the overspeed running of the exchangeable rotor is protected with a feed back loop from the magnet 214, the master microprocessor 211 or the salve microprocessor 205, an OR gate 208, the switch circuit 207, and the motor 202, wherein the master microprocessor 211 and the slave microprocessor 205 are doubled with respect to feedback loops. Therefore, a runaway in the master microprocessor 211 or the slave microprocessor 205 and an erroneous operation due to a bug in a program in the master microprocessor 211 or the slave microprocessor 205 can be avoided. However, the feed back loop is single.